This invention relates in general to non-contact temperature measuring techniques and in particular, to a non-contact temperature measuring technique and apparatus for measuring the temperature of an object from radiation heat flow emitted from the object.
It is well known that when two objects are placed in close proximity to each other, they will thermally interact through heat exchange until both objects come to thermal equilibrium, and that the magnitude of the heat flow between the two objects during such periods is related to their temperature differential.
Heat exchange between two objects can occur by any one or a combination of the methods of conduction, convection or radiation. Conventional temperature measuring techniques employ at least one of these methods when determining the temperature of an object by bringing the object in close proximity to at least one reference body of known temperature. Whereas conduction is generally used in contact temperature measuring techniques, convection is often used in non-contact temperature measuring techniques.
U.S. Pat. No. 5,216,625 entitled "Autocalibrating Dual Sensor Non-Contact Temperature Measuring Device," issued to the inventor of the present invention, and incorporated herein by reference, describes a technique and apparatus using convection heat flow measurements for determining the temperature of a moving object by proximately positioning dual thermal sinks or reference bodies along a line of travel of the moving object. Thermally connected to each reference body is a temperature sensor and a heat flow sensor whose sensing surface is facing the line of travel of the moving object. Each heat flow sensor is positioned such that it is primarily responsive to the convection heat flow generated as a result of the moving object being at a different temperature than the heat flow sensor and its respective reference body. By maintaining a temperature differential between the dual reference bodies, by positioning them and their respective heat flow sensors such that they are equidistant from the line of travel of the moving object, and by calibrating their respective heat flow sensors such that they have the same sensitivity, the temperature of the moving object is calculated from the following equation: ##EQU1## where T.sub.obj is the temperature of the moving object, T.sub.1 and V.sub.1 are, respectively, the temperature of one of the reference bodies and the calibrated output voltage of its heat flow sensor, and T.sub.2 and V.sub.2 are, respectively, the temperature of the other reference body and the calibrated output voltage of its heat flow sensor.